Rockwell-automation Logix5000 Controllers Structured Text Programming Uživatelský manuál stáhnout pdf (Strana 14)

14 Publication 1756-PM007D-EN-P - November 2012

Chapter 1 Program Structured Text

In structured text, you use two types of expressions:

BOOL expression: An expression that produces either the BOOL value of 1

(true) or 0 (false).

• A bool expression uses bool tags, relational operators, and logical

operators to compare values or check if conditions are true or false.

For example, tag1>65.

• A simple bool expression can be a single BOOL tag.

• Typically, you use bool expressions to condition the execution of other

logic.

Numeric expression: An expression that calculates an integer or

floating-point value.

• A numeric expression uses arithmetic operators, arithmetic functions,

and bitwise operators. For example, tag1+5.

• Often, you nest a numeric expression within a bool expression. For

example, (tag1+5)>65.

Use the following table to choose operators for your expressions:

If you want to Then

Calculate an arithmetic value Use Arithmetic Operators and Functions on page 15.

Compare two values or strings Use Relational Operators on page 16.

Check if conditions are true or false Use Logical Operators on page 18.

Compare the bits within values Use Bitwise Operators on page 19.

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Rockwell-automation Logix5000 Controllers Structured Text Programming Uživatelský manuál Strana 14